1. Field of the Invention
The present invention relates to a repair structure and an active device array substrate, and more particularly, to a repair structure that can increase the repair yield and an active device array substrate that has a higher repair yield.
2. Description of Related Art
Although the technique of fabricating liquid crystal display is quite mature, defects are frequently produced in the process of fabricating the liquid crystal display panel. These defects in the liquid crystal display often cause discomfort to the user when an image is displayed. If all the defective liquid crystal display panels are directly scrapped, the manufacturing cost of the display panels will be significantly increased. In general, relying only on the improvement in the fabricating technique to achieve a zero defect rate is very difficult. Therefore, the technique for repairing defects in the liquid crystal display panel has become critical. In the conventional technique, defects in the liquid crystal display panel are repaired either by laser welding or laser cutting.
Typically, a liquid crystal display mainly includes a liquid crystal display panel and a back light module. The liquid crystal display panel mainly includes a thin film transistor array substrate and a color filter substrate. In the process of fabricating the thin film transistor array substrate, broken line defects are frequently produced. These broken line defects can be detected in an array test and can be repaired in a repair process by performing a laser chemical vapor deposition (laser CVD). However, not all of the broken line defects are suitable for a repair using the laser CVD process. For example, the broken line defects cannot be repaired in this way if the broken line defects are discovered after liquid crystal cells are assembled.
In addition, if the broken line defects are discovered after the thin film transistor array substrate and the color-filter substrate (not shown) are assembled together and liquid crystal (not shown) is injected, the laser CVD process cannot be used to perform a repair above the broken line because the thin film transistor array where the broken line occurs has already been entirely enclosed within the liquid crystal cell. To prevent the formation of any bright lines on the liquid crystal display panel (not shown), other repair methods, for example, using the repair lines of the thin film transistor array substrate, must be used to repair the liquid crystal display panel.
FIG. 1A is a top view of the structure of a conventional thin film transistor array substrate. FIG. 1B is a schematic cross-sectional view along line A-A′ of FIG. 1A. As shown in FIG. 1A, the thin film transistor array substrate 100 includes a substrate 110, a plurality of scan lines 120, a plurality of data lines 130, a plurality of pixel units 140 and a repair line 150. The scan lines 120, the data lines 130, the pixel units 140 and the repair line 150 are disposed over the substrate 110. Each of the pixel units 140 includes a thin film transistor 142 and a transparent conductive electrode, for example, an indium tin oxide (ITO) electrode 144. The thin film transistor 142 is electrically connected to one of the scan lines 120 and one of the data lines 130 correspondingly, and the indium tin oxide electrode 144 is electrically connected to one of the active devices 140 correspondingly.
After assembling the thin film transistor array substrate 100 and a color-filter substrate and injecting a liquid crystal into the space between them, a liquid crystal display panel is formed. However, if broken line defects are detected on the thin film transistor array substrate 100, a repair is performed through the repair line 150. For example, when a broken data line 130 is detected on the thin film transistor array substrate 100, a laser can be used to fuse the contacts 150a and 150b and connect the repair line 150 and the data line 130. Hence, through the repair line 150, most of the functions of the damaged data line 130 are reconstituted.
As shown in FIG. 1B, it should be noted that there is an insulating layer 162, an amorphous silicon layer 164 and a doped amorphous silicon layer 166 between the data line 130 and the repair line 150 and there is a protective layer 168 covering the data line 130. The thickness of the insulating layer 162, the amorphous silicon layer 164 and the doped amorphous silicon layer 166 is about 3500 Å (angstroms) to 8500 Å. When the laser is used to fuse and connect the data line 130 and the repair line 150, the laser would hardly burn through to the repair line 150 due to the greater total thickness of the film layers between the data line 130 and the repair line 150. As a result, the data line 130 and the repair line 150 may form a poor electrical contact or the data line 130 and the repair line 150 may not fuse together, thereby leading to a lowering of the repair yield.